One of the major complications resulting from diabetes mellitus is a thickening of basement membranes in many different parts of the body. Although thickened, these basement membranes are apparently more permeable. This suggests that the intrinsic nature of basement membranes is altered in the diabetic state. So far, only partial characterizations of ocular basement membranes have been performed. In view of the fact that diabetes is one of the leading causes of blindness, it is important to more fully characterize ocular basement membranes. The objective of the proposed research is to determine the effect of diabetes on the composition and subunit structure of retinal capillary basement membrane and lens capsule. The amino acid, carbohydrate, and hydroxylysine glycoside content of these ocular membranes will be determined. The membranes will be solubilized and the subunits separated on the basis of size and charge. The composition of selected subunits, particularly those, if any, that are altered as a result of diabetes, will be determined. Membranes from humans and from animals with induced diabetes will be studied. The duration of diabetes will be correlated with biochemical and morphological data. It is hoped that this characterization of the effects of diabetes on ocular basement membranes will be helpful in efforts to minimize the complications arising from this disease.